Published online by Cambridge University Press: 22 October 2009
Approximately one in four male patients attending infertility clinics possess an overt defect in their semen profile (Hull et al., 1985).
The paucity of human semen quality sets us apart from most, if not all, other mammalian species. Even in normal fertile men a majority of the spermatozoa may exhibit abnormalities in their morphology and motility.
The first step in the laboratory assessment of male fertility is to create a traditional semen profile according to the criteria set out in the World Health Organization's laboratory manual for the examination of human semen and sperm–cervical interaction (World Health Organization, 1999). This analysis consists of a preliminary macroscopic examination of the semen followed by a detailed microscopic assessment of the cellular components of the ejaculate (Figure 3.1).
The initial macroscopic investigation of semen should take account of the volume of the ejaculate, the completeness of liquefaction viscosity, odour, colour, and the presence of blood, gelatinous bodies and mucous streaks. Contamination with urine, as may happen with patients exhibiting disturbances of bladder neck function, results in a yellow discoloration of the sample. Yellow discoloration of the semen is also common in jaundiced patients.
The consistency of the semen, also known as viscosity, refers to the fluid nature of the entire sample (Figure 3.2). Highly viscous samples are difficult to analyse and are associated with infertility since the migration of the spermatozoa into cervical mucus is impaired.
Particular attention should also be paid to the liquefaction status of the semen. Under normal circumstances a human semen sample should coagulate on ejaculation and then liquefy within 5–15 minutes at room temperature.